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Pearcey GEP, Afsharipour B, Holobar A, Sandhu MS, Rymer WZ. Acute intermittent hypoxia increases maximal motor unit discharge rates in people with chronic incomplete spinal cord injury. J Physiol 2024. [PMID: 39058666 DOI: 10.1113/jp285049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Accepted: 06/17/2024] [Indexed: 07/28/2024] Open
Abstract
Acute intermittent hypoxia (AIH) is an emerging technique for enhancing neuroplasticity and motor function in respiratory and limb musculature. Thus far, AIH-induced improvements in strength have been reported for upper and lower limb muscles after chronic incomplete cervical spinal cord injury (iSCI), but the underlying mechanisms have been elusive. We used high-density surface EMG (HDsEMG) to determine if motor unit discharge behaviour is altered after 15 × 60 s exposures to 9% inspired oxygen, interspersed with 21% inspired oxygen (AIH), compared to breathing only 21% air (SHAM). We recorded HDsEMG from the biceps and triceps brachii of seven individuals with iSCI during maximal elbow flexion and extension contractions, and motor unit spike trains were identified using convolutive blind source separation. After AIH, elbow flexion and extension torque increased by 54% and 59% from baseline (P = 0.003), respectively, whereas there was no change after SHAM. Across muscles, motor unit discharge rates increased by ∼4 pulses per second (P = 0.002) during maximal efforts, from before to after AIH. These results suggest that excitability and/or activation of spinal motoneurons is augmented after AIH, providing a mechanism to explain AIH-induced increases in voluntary strength. Pending validation, AIH may be helpful in conjunction with other therapies to enhance rehabilitation outcomes after incomplete spinal cord injury, due to these enhancements in motor unit function and strength. KEY POINTS: Acute intermittent hypoxia (AIH) causes increases in muscular strength and neuroplasticity in people living with chronic incomplete spinal cord injury (SCI), but how it affects motor unit discharge rates is unknown. Motor unit spike times were identified from high-density surface electromyograms during maximal voluntary contractions and tracked from before to after AIH. Motor unit discharge rates were increased following AIH. These findings suggest that AIH can facilitate motoneuron function in people with incomplete SCI.
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Affiliation(s)
- Gregory E P Pearcey
- School of Human Kinetics and Recreation, and Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Babak Afsharipour
- Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Aleš Holobar
- Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Milap S Sandhu
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Shirley Ryan AbilityLab, Chicago, IL, USA
| | - W Zev Rymer
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Shirley Ryan AbilityLab, Chicago, IL, USA
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Debenham MIB, Franz CK, Berger MJ. Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations. Muscle Nerve 2024; 70:12-27. [PMID: 38477416 DOI: 10.1002/mus.28070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 02/13/2024] [Accepted: 02/17/2024] [Indexed: 03/14/2024]
Abstract
The spinal cord facilitates communication between the brain and the body, containing intrinsic systems that work with lower motor neurons (LMNs) to manage movement. Spinal cord injuries (SCIs) can lead to partial paralysis and dysfunctions in muscles below the injury. While traditionally this paralysis has been attributed to disruptions in the corticospinal tract, a growing body of work demonstrates LMN damage is a factor. Motor units, comprising the LMN and the muscle fibers with which they connect, are essential for voluntary movement. Our understanding of their changes post-SCI is still emerging, but the health of motor units is vital, especially when considering innovative SCI treatments like nerve transfer surgery. This review seeks to collate current literature on how SCI impact motor units and explore neuromuscular clinical implications and treatment avenues. SCI reduced motor unit number estimates, and surviving motor units had impaired signal transmission at the neuromuscular junction, force-generating capacity, and excitability, which have the potential to recover chronically, yet the underlaying mechanisms are unclear. Furthermore, electrodiagnostic evaluations can aid in assessing the health lower and upper motor neurons, identify suitable targets for nerve transfer surgeries, and detect patients with time sensitive injuries. Lastly, many electrodiagnostic abnormalities occur in both chronic and acute SCI, yet factors contributing to these abnormalities are unknown. Future studies are required to determine how motor units adapt following SCI and the clinical implications of these adaptations.
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Affiliation(s)
- Mathew I B Debenham
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Colin K Franz
- Biologics Laboratory, Shirley Ryan AbilityLab, Chicago, Illinois, USA
- Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
- Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Michael J Berger
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Division of Physical Medicine & Rehabilitation, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Potter-Baker KA, Janini DP, Lin YL, Sankarasubramanian V, Cunningham DA, Varnerin NM, Chabra P, Kilgore KL, Richmond MA, Frost FS, Plow EB. Transcranial direct current stimulation (tDCS) paired with massed practice training to promote adaptive plasticity and motor recovery in chronic incomplete tetraplegia: A pilot study. J Spinal Cord Med 2018; 41:503-517. [PMID: 28784042 PMCID: PMC6117576 DOI: 10.1080/10790268.2017.1361562] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVE Our goal was to determine if pairing transcranial direct current stimulation (tDCS) with rehabilitation for two weeks could augment adaptive plasticity offered by these residual pathways to elicit longer-lasting improvements in motor function in incomplete spinal cord injury (iSCI). DESIGN Longitudinal, randomized, controlled, double-blinded cohort study. SETTING Cleveland Clinic Foundation, Cleveland, Ohio, USA. PARTICIPANTS Eight male subjects with chronic incomplete motor tetraplegia. INTERVENTIONS Massed practice (MP) training with or without tDCS for 2 hrs, 5 times a week. OUTCOME MEASURES We assessed neurophysiologic and functional outcomes before, after and three months following intervention. Neurophysiologic measures were collected with transcranial magnetic stimulation (TMS). TMS measures included excitability, representational volume, area and distribution of a weaker and stronger muscle motor map. Functional assessments included a manual muscle test (MMT), upper extremity motor score (UEMS), action research arm test (ARAT) and nine hole peg test (NHPT). RESULTS We observed that subjects receiving training paired with tDCS had more increased strength of weak proximal (15% vs 10%), wrist (22% vs 10%) and hand (39% vs. 16%) muscles immediately and three months after intervention compared to the sham group. Our observed changes in muscle strength were related to decreases in strong muscle map volume (r=0.851), reduced weak muscle excitability (r=0.808), a more focused weak muscle motor map (r=0.675) and movement of weak muscle motor map (r=0.935). CONCLUSION Overall, our results encourage the establishment of larger clinical trials to confirm the potential benefit of pairing tDCS with training to improve the effectiveness of rehabilitation interventions for individuals with SCI. TRIAL REGISTRATION NCT01539109.
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Affiliation(s)
- Kelsey A. Potter-Baker
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA,Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veteran’s Affairs, Cleveland, Ohio, USA
| | - Daniel P. Janini
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Yin-Liang Lin
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | | | - David A. Cunningham
- Kessler Foundation, Human Performance & Engineering Laboratory, West Orange, New Jersey, USA
| | - Nicole M. Varnerin
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Patrick Chabra
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Kevin L. Kilgore
- Functional Electrical Stimulation Center, Louis Stokes Cleveland Department of Veteran’s Affairs, Cleveland, Ohio, USA,Department of Orthopaedics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA,Department of Orthopaedics, MetroHealth Medical Center, Cleveland, Ohio, USA
| | - Mary Ann Richmond
- Spinal Cord Injury and Disorders Service, Louis Stokes Cleveland Department of Veteran’s Affairs, Cleveland, Ohio, USA,Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Frederick S. Frost
- Department of Physical Medicine and Rehabilitation, Neurological Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Ela B. Plow
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA,Department of Physical Medicine and Rehabilitation, Neurological Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA,Center for Neurological Restoration, Neurosurgery, Neurological Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA,Correspondence to: Ela B. Plow Assistant Staff, Department of Biomedical Engineering, Assistant Professor, Cleveland Clinic Lerner College of Medicine, Cleveland Clinic Foundation, 9500 Euclid Ave., ND20 Cleveland, OH 44195, USA; Ph: 216-445-4589, Fax: 216-444-9198;
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A nociceptive stress model of adolescent physical abuse induces contextual fear and cingulate nociceptive neuroplasticities. Brain Struct Funct 2017; 223:429-448. [PMID: 28861709 DOI: 10.1007/s00429-017-1502-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 08/18/2017] [Indexed: 10/19/2022]
Abstract
Adolescent physical abuse impairs emotional development and evokes cingulate pathologies, but its neuronal and circuit substrates are unknown. Conditioning adolescent rabbits with noxious colorectal distension for only 2 h over 3 weeks simulated the human child abuse in amplitude, frequency, and duration. Thermal withdrawal thresholds were unchanged suggesting that sensitized spinal mechanisms may not be operable. Unchanged weight, stools, colorectal histology, and no evidence of abdominal pain argue against tissue injury or irritable bowel syndrome. Contextual fear was amplified as they avoided the site of their abuse. Conditioning impacted anterior cingulate and anterior midcingulate (ACC, aMCC) neuron excitability: (1) more neurons responded to cutaneous and visceral (VNox) noxious stimuli than controls engaging latent nociception (present but not manifest in controls). (2) Rear paw stimulation increased responses over forepaws with shorter onsets and longer durations, while forepaw responses were of higher amplitude. (3) There were more VNox responses with two excitatory phases and longer durations. (4) Some had unique three-phase excitatory responses. (5) Long-duration VNox stimuli did not inhibit neurons as in controls, suggesting the release of an inhibitory circuit. (6) aMCC changes in cutaneous but not visceral nociception confirmed its role in cutaneous nociception. For the first time, we report neuroplasticities that may be evoked by adolescent physical abuse and reflect psychogenic pain: i.e., no ongoing peripheral pain and altered ACC nociception. These limbic responses may be a cognitive trace of abuse and may shed light on impaired human emotional development and sexual function.
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Reliability of TMS metrics in patients with chronic incomplete spinal cord injury. Spinal Cord 2016; 54:980-990. [DOI: 10.1038/sc.2016.47] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 02/18/2016] [Accepted: 02/28/2016] [Indexed: 12/26/2022]
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Abstract
BACKGROUND Short- (SICI) and long-interval intracortical inhibition (LICI) are involved in the control of movement and movement initiation. Alterations to the two circuits can result in direct alterations to the physiology of the muscles and can be used to explain the physiological changes to individuals with spinal cord injury (SCI). OBJECTIVE To probe changes in GABAergic function by characterizing the recruitment curves of SICI and LICI interval intracortical inhibition in an upper limb muscle in chronic SCI participants with injury between C3 and C7. METHODS Recruitment curves were elicited with conditioning stimulus intensities determined as a percentage of active motor threshold (AMT) (SICI, 60% to 110% AMT; LICI, 90% to 130% AMT) and recorded from the flexor carpi radialis muscle during an isometric contraction equal to 15% to 20% of maximum voluntary contraction. RESULTS AMT was greater and motor-evoked potential sizes were lower in SCI compared with uninjured controls. SICI magnitude was not different between groups, although the range of conditioning stimulus intensities to evoke SICI was unique to each group. LICI was reduced in the control group during active contraction and remained present in SCI. DISCUSSION LICI was increased in the actively contracted flexor carpi radialis muscle in individuals with SCI compared with age-matched controls. These findings indicate that GABAB function mediating LICI is different in SCI versus controls. CONCLUSIONS Increased LICI in SCI may be attributed to the medication baclofen or to changes in the neural mechanisms controlling contraction-related modulation of the LICI circuit.
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Nardone R, Höller Y, Thomschewski A, Bathke AC, Ellis AR, Golaszewski SM, Brigo F, Trinka E. Assessment of corticospinal excitability after traumatic spinal cord injury using MEP recruitment curves: a preliminary TMS study. Spinal Cord 2015; 53:534-8. [PMID: 25665538 DOI: 10.1038/sc.2015.12] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 12/30/2014] [Accepted: 01/08/2015] [Indexed: 12/20/2022]
Abstract
STUDY DESIGN Transcranial magnetic stimulation study. OBJECTIVES To further investigate the corticospinal excitability changes after spinal cord injury (SCI), as assessed by means of transcranial magnetic stimulation (TMS). SETTING Merano (Italy) and Salzburg (Austria). METHODS We studied resting motor threshold (RMT), motor evoked potential (MEP) amplitude and recruitment curve in five subjects with good recovery after traumatic incomplete cervical SCI. RESULTS RMT did not differ significantly between patients and controls, whereas the slope of MEP recruitment curve was significantly increased in the patients. CONCLUSION This abnormal finding may represent an adaptive response after SCI. The impaired ability of the motor cortex to generate proper voluntary movement may be compensated by increasing spinal excitability. The easily performed measurement of MEP recruitment curve may provide a useful additional tool to improve the assessment and monitoring of motor cortical function in subjects with SCI. Increasing our knowledge of the corticospinal excitability changes in the functional recovery after SCI may also support the development of effective therapeutic strategies.
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Affiliation(s)
- R Nardone
- 1] Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria [2] Department of Neurology, Franz Tappeiner Hospital, Merano, Italy [3] Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
| | - Y Höller
- 1] Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria [2] Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
| | - A Thomschewski
- 1] Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria [2] Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
| | - A C Bathke
- 1] Department of Mathematics, Paris Lodron University, Salzburg, Austria [2] Department of Statistics, University of Kentucky, Lexington, KY, USA
| | - A R Ellis
- Department of Statistics, University of Kentucky, Lexington, KY, USA
| | - S M Golaszewski
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria
| | - F Brigo
- 1] Department of Neurology, Franz Tappeiner Hospital, Merano, Italy [2] Department of Neurological, Neuropsychological, Morphological and Movement Sciences, Section of Clinical Neurology, University of Verona, Verona, Italy
| | - E Trinka
- 1] Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria [2] Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
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Nardone R, Höller Y, Brigo F, Orioli A, Tezzon F, Schwenker K, Christova M, Golaszewski S, Trinka E. Descending motor pathways and cortical physiology after spinal cord injury assessed by transcranial magnetic stimulation: a systematic review. Brain Res 2014; 1619:139-54. [PMID: 25251591 DOI: 10.1016/j.brainres.2014.09.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 08/06/2014] [Accepted: 09/15/2014] [Indexed: 02/02/2023]
Abstract
We performed here a systematic review of the studies using transcranial magnetic stimulation (TMS) as a research and clinical tool in patients with spinal cord injury (SCI). Motor evoked potentials (MEPs) elicited by TMS represent a highly accurate diagnostic test that can supplement clinical examination and neuroimaging findings in the assessment of SCI functional level. MEPs allows to monitor the changes in motor function and evaluate the effects of the different therapeutic approaches. Moreover, TMS represents a useful non-invasive approach for studying cortical physiology, and may be helpful in elucidating the pathophysiological mechanisms of brain reorganization after SCI. Measures of motor cortex reactivity, e.g., the short interval intracortical inhibition and the cortical silent period, seem to point to an increased cortical excitability. However, the results of TMS studies are sometimes contradictory or divergent, and should be replicated in a larger sample of subjects. Understanding the functional changes at brain level and defining their effects on clinical outcome is of crucial importance for development of evidence-based rehabilitation therapy. TMS techniques may help in identifying neurophysiological biomarkers that can reliably assess the extent of neural damage, elucidate the mechanisms of neural repair, predict clinical outcome, and identify therapeutic targets. Some researchers have begun to therapeutically use repetitive TMS (rTMS) in patients with SCI. Initial studies revealed that rTMS can induce acute and short duration beneficial effects especially on spasticity and neuropathic pain, but the evidence is to date still very preliminary and well-designed clinical trials are warranted. This article is part of a Special Issue entitled SI: Spinal cord injury.
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Affiliation(s)
- Raffaele Nardone
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Department of Neurology, Franz Tappeiner Hospital, Merano, Via Rossini 5, 39012 Meran/o (BZ), Italy; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria.
| | - Yvonne Höller
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
| | - Francesco Brigo
- Department of Neurology, Franz Tappeiner Hospital, Merano, Via Rossini 5, 39012 Meran/o (BZ), Italy; Department of Neurological, Neuropsychological, Morphological and Movement Sciences, Section of Clinical Neurology, University of Verona, Italy
| | - Andrea Orioli
- Department of Neurology, Franz Tappeiner Hospital, Merano, Via Rossini 5, 39012 Meran/o (BZ), Italy
| | - Frediano Tezzon
- Department of Neurology, Franz Tappeiner Hospital, Merano, Via Rossini 5, 39012 Meran/o (BZ), Italy
| | - Kerstin Schwenker
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
| | - Monica Christova
- Department of Physiology, Medical University of Graz, Graz, Austria
| | - Stefan Golaszewski
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria
| | - Eugen Trinka
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University and Center for Cognitive Neuroscience, Salzburg, Austria; Spinal Cord Injury and Tissue Regeneration Center, Paracelsus Medical University, Salzburg, Austria
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Thomas CK, Bakels R, Klein CS, Zijdewind I. Human spinal cord injury: motor unit properties and behaviour. Acta Physiol (Oxf) 2014; 210:5-19. [PMID: 23901835 DOI: 10.1111/apha.12153] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 05/31/2013] [Accepted: 07/29/2013] [Indexed: 01/03/2023]
Abstract
Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI.
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Affiliation(s)
- C. K. Thomas
- The Miami Project to Cure Paralysis, Departments of Neurological Surgery, and Physiology and Biophysics; University of Miami; Miami FL USA
| | - R. Bakels
- Department of Neuroscience; University Medical Center Groningen; University of Groningen; Groningen the Netherlands
| | - C. S. Klein
- Rehabilitation Institute of Chicago; Chicago IL USA
| | - I. Zijdewind
- Department of Neuroscience; University Medical Center Groningen; University of Groningen; Groningen the Netherlands
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The Sir Ludwig Guttmann Lecture 2012: the contribution of Stoke Mandeville Hospital to spinal cord injuries. Spinal Cord 2012; 50:790-6. [DOI: 10.1038/sc.2012.109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Clinical neurophysiology in the prognosis and monitoring of traumatic spinal cord injury. HANDBOOK OF CLINICAL NEUROLOGY 2012; 109:63-75. [PMID: 23098706 DOI: 10.1016/b978-0-444-52137-8.00004-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Preclinical studies for the repair of spinal cord injury (SCI) and potential therapies for accessing the inherent plasticity of the central nervous system (CNS) to promote recovery of function are currently moving into the translational stage. These emerging clinical trials of therapeutic interventions for the repair of SCI require improved assessment techniques and quantitative outcome measures to supplement the American Spinal Injuries Association (ASIA) Impairment Scales. This chapter attempts to identify those electrophysiological techniques that show the most promise for provision of objective and quantitative measures of sensory, motor, and autonomic function in SCI. Reviewed are: (1) somatosensory evoked potentials, including dermatomal somatosensory evoked potentials, and the electrical perceptual threshold as tests of the dorsal (posterior) column pathway; (2) laser evoked potentials and contact heat evoked potentials as tests of the anterior spinothalamic tract; (3) motor evoked potentials in limb muscles, in response to transcranial magnetic stimulation of the motor cortex as tests of the corticospinal tract, and the application of the technique to assessment of trunk and sphincter muscles; and (4) the sympathetic skin response as a test of spinal cord access to the sympathetic chain.
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Roy FD, Zewdie ET, Gorassini MA. Short-interval intracortical inhibition with incomplete spinal cord injury. Clin Neurophysiol 2011; 122:1387-95. [DOI: 10.1016/j.clinph.2010.11.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 11/10/2010] [Accepted: 11/22/2010] [Indexed: 12/14/2022]
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Kuppuswamy A, Catley M, King NKK, Strutton PH, Davey NJ, Ellaway PH. Cortical control of erector spinae muscles during arm abduction in humans. Gait Posture 2008; 27:478-84. [PMID: 17644335 DOI: 10.1016/j.gaitpost.2007.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 04/25/2007] [Accepted: 06/09/2007] [Indexed: 02/02/2023]
Abstract
Abduction of one arm preferentially activates erector spinae muscles on the other side to stabilise the body. We hypothesise that the corticospinal drive to the arm abductors and the erector spinae may originate from the same hemisphere. In 18 subjects, transcranial magnetic stimulation (TMS) was applied using an angle double-cone coil placed symmetrically over the vertex. Motor evoked potentials (MEP) could not be evoked systematically seated at rest but could be evoked bilaterally in erector spinae muscles during unilateral arm abduction. TMS was applied at 110% and 120% motor threshold (MT) for the contralateral erector spinae muscle when an arm was abducted against resistance. The electromyographic (EMG) activity in the erector spinae at L4 vertebral level during contralateral arm abduction was significantly higher (P<0.05) than in the ipsilateral erector spinae. The mean (+/-S.E.M.) latencies of MEPs in the contralateral muscle to TMS at 120%MT (left 16.0+/-0.8 ms; right 17.0+/-0.8 ms) were significantly (P<0.05) longer than in the ipsilateral erector spinae (13.9+/-1.0 ms; 16.6+/-0.4 ms). In two of six subjects from the same group, it was possible to elicit MEPs by TMS applied selectively to one hemisphere using a figure-of-eight coil. MEPs ipsilateral to the TMS had longer latencies than contralateral MEPs. The study revealed an unexpectedly longer rather than shorter latency of the MEP recorded from the lumbar erector spinae muscles when co-activated during abduction of the opposite arm. A speculative explanation is that TMS might activate back muscles contralateral to arm abduction via an uncrossed, ipsilateral corticospinal tract that is slower conducting than the conventional crossed corticospinal tract. The study has implications for the design of measures to promote recovery and rehabilitation of motor function in disorders such as stroke and spinal cord injury.
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Affiliation(s)
- Annapoorna Kuppuswamy
- Division of Neuroscience and Mental Health, Imperial College London, Charing Cross Campus, London W6 8RP, UK
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Sikes RW, Vogt LJ, Vogt BA. Distribution and properties of visceral nociceptive neurons in rabbit cingulate cortex. Pain 2007; 135:160-74. [PMID: 18022321 DOI: 10.1016/j.pain.2007.09.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 07/18/2007] [Accepted: 09/24/2007] [Indexed: 10/22/2022]
Abstract
Human imaging localizes most visceral nociceptive responses to anterior cingulate cortex (ACC), however, imaging in conscious subjects cannot completely control anticipatory and reflexive activity or resolve neuron activity. This study overcame these shortcomings by recording individual neuron responses in 12 anesthetized and paralyzed rabbits to define the visceronociceptive response pattern by region and layer. Balloon distension was applied to the colon at innocuous (15 mmHg) or noxious (60 mmHg) intensities, and innocuous and noxious mechanical, thermal and electrical stimuli were applied to the skin. Simultaneous recording from multiple regions assured differences were not due to anesthesia and neuron responses were resolved by spike sorting using principal components analysis. Of the total 346 neurons, 48% were nociceptive; responding to noxious levels of visceral or cutaneous stimulation, or both. Visceronociceptive neurons were most frequent in ACC (39%) and midcingulate cortex (MCC, 36%) and infrequent in retrosplenial cortex (RSC, 12%). In contrast, cutaneous nociceptive units were higher in MCC (MCC, 43%; ACC, 32%; RSC, 23%). Visceral-specific neurons were proportionately more frequent in ACC (37%), while cutaneous-specific units predominated in RSC (62.5%). Visceral nociceptive response durations were longer than those for cutaneous responses. Postmortem analysis of electrode tracks confirmed regional designations, and laminar analysis found inhibitory responses mainly in superficial layers and excitatory in deep layers. Thus, cingulate visceral nociception extends beyond ACC, this is the first report of nociceptive activity in RSC including nociceptive cutaneous responses, and these regional differences require a new model of cingulate nociceptive processing.
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Affiliation(s)
- Robert W Sikes
- Northeastern University, Department of Physical Therapy, 360 Huntington Avenue, Boston, MA 02115, USA.
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Patil PG, Carmena JM, Nicolelis MA, Turner DA. Ensemble Recordings Of Human Subcortical Neurons as a Source Of Motor Control Signals For a Brain-Machine Interface. Neurosurgery 2004. [DOI: 10.1227/01.neu.0000126872.23715.e5] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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16
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Strutton PH, Catley M, McGregor AH, Davey NJ. Corticospinal excitability in patients with unilateral sciatica. Neurosci Lett 2003; 353:33-6. [PMID: 14642431 DOI: 10.1016/j.neulet.2003.09.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patients suffering from sciatica may develop altered patterns of corticospinal drive to muscles of the leg. Electromyographic recordings were made bilaterally from tibialis anterior and lateral gastrocnemius muscles during transcranial magnetic stimulation of the motor cortex from nine patients with unilateral sciatica and seven healthy controls. The mean thresholds for eliciting motor evoked potentials (MEPs) and the silent period were higher in the patients than in the control subjects. In addition, there was a positive correlation between the patients' self rated score of disability (the Oswestry Disability Index) and their threshold for MEPs and the silent period. This study suggests that the chronic pain experienced by the patients leads to a reduction in corticospinal drive to the legs. These changes might help to relax muscles close to the perceived site of pain and so alleviate symptoms. Investigation of these patients following remedial treatment will allow us to establish if the changes are transient in nature.
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Affiliation(s)
- Paul H Strutton
- Department of Sensorimotor Systems, Division of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College London, Charing Cross Campus, London W6 8RP, UK.
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17
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Chapter 8 Transcranial magnetic stimulation. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-4231(09)70156-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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18
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Cariga P, Catley M, Nowicky AV, Savic G, Ellaway PH, Davey NJ. Segmental recording of cortical motor evoked potentials from thoracic paravertebral myotomes in complete spinal cord injury. Spine (Phila Pa 1976) 2002; 27:1438-43. [PMID: 12131743 DOI: 10.1097/00007632-200207010-00013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN A study of thoracic paravertebral muscle motor-evoked potentials using transcranial magnetic stimulation in spinal cord injury patients and control participants. OBJECTIVES To develop a method to study the level and density of corticospinal lesions in thoracic spinal cord injury. SUMMARY OF BACKGROUND DATA Cervical and lumbar spinal cord injury, unlike thoracic spinal cord injury, can be quantified by recording muscle motor-evoked potentials from limb muscles. For thoracic spinal cord injury, the use of paravertebral muscles is limited by complex innervation patterns and the greater difficulty in obtaining muscle motor-evoked potentials. METHODS In 10 patients with complete midthoracic spinal cord injury (T4-T7) and 10 age-matched control participants, muscle motor-evoked potentials were recorded from all thoracic paravertebral muscles using transcranial magnetic stimulation with a double-cone stimulating coil over the vertex. RESULTS In control participants, muscle motor-evoked potential responses evoked in all myotomes had progressively increasing latency in a rostrocaudal direction. Threshold was comparable in all segments. The duration of muscle motor-evoked potentials was unrelated to the spinal level. In spinal cord injury, responses were elicited in all segments above a lesion and in a varying range of segments below the lesion. In comparison with control participants, threshold was lower above and higher below the lesion (P < 0.001) in patients with spinal cord injury. Latency was longer than normal both above and below the lesion (P < 0.001). Duration was not significantly different from that in control participants at any level. CONCLUSIONS Paravertebral muscle motor-evoked potentials can be elicited below the level of a complete spinal cord injury. Possible reasons for this include the multisegmental innervation of these muscles and the long muscle fiber conduction. Stretch reflex activation elicited by contraction of muscles above the lesion is thought to be an unlikely mechanism because of the latency of the response. Although the presence or absence of muscle motor-evoked potentials does not appear to be a sensitive indicator of the level of thoracic spinal cord injury lesion, analysis of muscle motor-evoked potentials reveals abnormal patterns that may assist in defining lesions. Finally, lower threshold above the lesion suggests corticospinal hyperexcitability of this pathway as a result of central plasticity after spinal cord injury.
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Affiliation(s)
- Pietro Cariga
- Department of Sensorimotor Systems, Faculty of Medicine, Imperial College School of Science, Technology and Medicine, Charing Cross Hospital, London, United Kingdom
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Hornby TG, McDonagh JC, Reinking RM, Stuart DG. Motoneurons: A preferred firing range across vertebrate species? Muscle Nerve 2002; 25:632-648. [PMID: 11994957 DOI: 10.1002/mus.10105] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The term "preferred firing range" describes a pattern of human motor unit (MU) unitary discharge during a voluntary contraction in which the profile of the spike-frequency of the MU's compound action potential is dissociated from the profile of the presumed depolarizing pressure exerted on the unit's spinal motoneuron (MN). Such a dissociation has recently been attributed by inference to the presence of a plateau potential (PP) in the active MN. This inference is supported by the qualitative similarities between the firing pattern of human MUs during selected types of relatively brief muscle contraction and that of intracellularly stimulated, PP-generating cat MNs in a decerebrate preparation, and turtle MNs in an in vitro slice of spinal cord. There are also similarities between the stimulus-response behavior of intracellularly stimulated turtle MNs and human MUs during the elaboration of a slowly rising voluntary contraction. This review emphasizes that there are a variety of open issues concerning the PP. Nonetheless, a rapidly growing body of comparative vertebrate evidence supports the idea that the PP and other forms of non-linear MN behavior play a major role in the regulation of muscle force, from the lamprey to the human.
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Affiliation(s)
- T George Hornby
- Department of Physiology, The University of Arizona College of Medicine, Tucson, Arizona 85724-5051, USA
| | - Jennifer C McDonagh
- Department of Physiology, The University of Arizona College of Medicine, Tucson, Arizona 85724-5051, USA
| | - Robert M Reinking
- Department of Physiology, The University of Arizona College of Medicine, Tucson, Arizona 85724-5051, USA
| | - Douglas G Stuart
- Department of Physiology, The University of Arizona College of Medicine, Tucson, Arizona 85724-5051, USA
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Ioannides AA, Liu L, Khurshudyan A, Bodley R, Poghosyan V, Shibata T, Dammers J, Jamous A. Brain activation sequences following electrical limb stimulation of normal and paraplegic subjects. Neuroimage 2002; 16:115-29. [PMID: 11969323 DOI: 10.1006/nimg.2002.1065] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In current clinical practice the degree of paraplegia or quadriplegia is objectively determined with transcranial magnetic stimulation (TMS) and somatosensory-evoked potentials (SSEP). We measured the MEG signal following electrical stimulation of upper and lower limbs in two normal and three clinically complete paraplegic subjects. From the MEG signal we computed distributed estimates of brain activity and identified foci just behind the central sulcus consistent in location with primary somatosensory (SI) for arm and foot and secondary somatosensory (SII) areas. Activation curves were computed from regions of interest defined around these areas. Activation of the SI foot area was observed in normal and paraplegic subjects when the upper limb was stimulated. Surprisingly, for each paraplegic subject, stimulation below the lesion was followed by cortical activations. These activations were weak, only loosely time-locked to the stimulus and were seen intermittently behind the central sulcus and nearby cortical areas. Statistical analysis of tomographic solutions and activation curves showed consistent responses following foot stimulation in one paraplegic (PS1) and intermittently in another paraplegic subject. We repeated the same experiment for PS1 in a different laboratory and the results from the analysis of foot stimulation from both laboratories revealed statistically significant focal cortical response only in the contralateral SI foot area.
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Affiliation(s)
- Andreas A Ioannides
- Laboratory for Human Brain Dynamics, Brain Science Institute (BSI), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
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